Hello!

We actually have a webcam working with linux perfectly (its the Logitech 961404 Quickcam for Notebooks).

Picture is nice, speed is ok.

But now we would like to use this webcam for getting a picture from outside the window. As we tried this we noticed that the webcam is not build to get pictures from objects which a more then lets say 20m away.

question:

a) Does anybody here use a cheep webcam which could be used for such a task ?
b) Am I doing anything wrong ? which i don`t believe as the close pictures are perfekt.

thankes so far.

Cheap webcams, like cameras, have a simple plastic (spherical) lense which is usually good for 1-2m tops. You'll also get distortion at extreme close range. This is entirely due to the optical properties of the lense/CCD arrangement.

The usual approach is to place a lens system in front of the camera. A simple bi-concave lens with a focal length 10-20cm will probably do. If you can tell me the effective far-point and the desired far-point, I can be more precise.

Cameras built for security applications are often good, and, of course, those built for astronomy have special support for being fixed to telescopes.

Well, thanks for your fast answer...

I am not so sure which infos are missing.

I would like to use the webcam from a high building in our company to documente a new building beeing build.

The distance might be about 300-500m away.

I have a logitech here with a neerpoint within 10cm and a farpoint too far for me to conveniently measure, 20m seems about right. You could (naively) treat it as a short-sighted eyeball and add a lens so that an object a long way away produces an image at the farpoint. Since 500m >> 20m, a focal length of 20m will do it.

There is more to getting a clear image than that, but it is a simple place to start - mind you, I have a stack of lenses at my elbow. You may find it trickier.

Converging lenses are easy to get hold of (magnifying glass) but you may have to try a camera shop for diverging ones. (Glass, biconcave, lenses are "diverging" in air.) The proprietor will have a better idea of what you can try than I will as his stock is right there.

I doubt a security camera will perform well over 300-500m ... have you tried just pointing the camera through one objective of binoculars?

I suspect, though, that you are just happy with a nice picture from a distance. That's why I suggested 10-20cm ... these are usually quite cheap and may clear the picture enough.

so i think your absolutely right. befor i trie to "build" some kind of linses and so on it my be the better soulution to by an other camera.

so i am just wondering, which one ? any ideas ?

If you can get a good deal on an old video camera you could use that if you had a video capture card..


I use an old Sony handicam that I bought years and years ago for a webcam. I had it set up inside my office window and it had a clear picture of objects that were across the street that runs in front of my house. The image/video quality was far superior to any computer webcam I've seen.

well.... i ` am sure your right, but i don`t have a tv-card nor a video camera.

Looking at the specs for some of Logitech's latest webcams I see many are described as 'fixed focus'.

But I have a Logitech Quickcam IM (works with gspca driver) and it has a focus ring around the lens. It will focus down to about 1.5cm. I am not sure how far it goes in the other direction as I have no view of distant objects at this location. It would certainly be strange if the design did not let focus extend to infinity.

The docs for the camera make no reference to the focus ring, except to label it in a picture of the cam.

I see there is now a Logitech webcam with autofocus (Pro 9000). No sign of a linux driver unfortunately. If the autofocus is handled in the driver software it would be a big challenge to produce a linux driver without support from Logitech.

... by which you mean that it will resolve images of objects 1.5cm away. The infinity setting means that parallel light converges to the CCD surface.

I have the same camera. I think I really have to play with this... but it is easy to add a lens that puts the far-point an arbitrary distance away. Some cameras will, however, suffer from depth-of-field problems.

... but you asked for suggestions concerning what cameras to buy, didn't you? Or do you only want reviews of hardware you currently possess?
... this is correct. Wub-cams are not very useful for the task you are set. Video cameras are better. Some brands will connect to your computer using a usb port, but you are better off with a TV input since almost all cameras will play direct to a TV set.

Here's an example using firewire:
http://www.jennings.homelinux.net/video_camera.html

The cameras main advantage is that they come with a complex lens system that will take care of all the above for you. Look for second-hand cameras and second hand nvidia cards. Should be cheaper than a new webcam.

Sie sollten ein Objektiv improvisieren oder eine videokamera kaufen.

If I wanted to record a building going up, I would look for a cheap digital still camera with time-lapse recording and external power supply. At 1 picture per hour it would take at least a month to fill up a 1GB memory card. The quality would be far superior to anything you would get with a web or video cam.

i have an integrated web cam in my laptop acer amd 64. the cam has resolution 1.3 mp. how to know its model no. and whether it works with fedora 7 or not. please help me.

You should probably start a new thread. Your question if off-topic on this thread so it may not be read by anybody who knows about your hardware.

One thing you can do straight away is run the command 'lsusb' and look for a section in there which describes your camera that you can include in your next post.

EDIT: OK I see you did start a new thread. Suggest you add any information from lsusb to that.

thanks everybody so far...i`am still looking for a way...

I don't think it is possible with a webcam, not with good results. Buy a relatively cheap camera (not a webcam) and try if that works!